Doubling sound intensity raises the decibel level by exactly 3 dB

Evidence

Thus, a 0 dB sound (the logarithm of 1 is 0) is barely audible to those with excellent hearing in a perfectly quiet environment. Since 10 log10(2) ≈ 3, a doubling of sound intensity (for example, two identical instruments instead of one) corresponds to a 3 dB increase. This definition makes clear that a 10 dB increase in sound intensity (measured in dB) corresponds to a ten-fold increase in power. The buzz of a nearby mosquito is about 40 dB, and a normal conversation is about 60 dB. There is 100 times more power in a normal conversational voice than in a mosquito buzz. Still, the mosquito is surprisingly loud, considering a human weighs 10 million times as much as a mosquito. — Eric J. Heller, Why You Hear What You Hear- An…, 225

Categorization

• DEFINE: Defines the dB scale concretely: 0 dB = hearing threshold, 10 dB = tenfold power, 3 dB = doubling.
• CANDY: The 40 dB mosquito buzz vs 60 dB conversation, with the 10-million-weight ratio, is a fun elevator fact.